Many methods of welding are known in the art, each with its own advantages and disadvantages. Common welding processes include gas welding, oxyacetylene brazing and soldering, shielded metal arc welding (SMAW) or "STICK" welding, metal inert gas (MIG) or "wire feed" welding, gas tungsten arc welding (GTAW) or TIG welding, and plasma cutting. Each welding process requires special equipment that the welder uses to perform the welding operation. Some of this equipment can be used for multiple welding operations. The preferred embodiment of the present invention is directed to a welding device including a welding power source adapted for both STICK and TIG welding processes, though the present invention will surely find applications in devices for other welding processes.
Both STICK and TIG welding processes require generation of a high-current electrical arc between an electrode and a base metal or workpiece. This current is supplied by a welding power source. When performing a TIG welding process, the welder holds a torch having a tungsten electrode and a channel for dispensing a protective inert gas to the welding site. The welder strikes an arc and feeds a bare welding rod to the welding site, thereby creating a molten puddle. The molten puddle hardens to leave a weld bead joining two pieces of metal. STICK welding is similar, except that the electrode is a stick electrode coated with flux. The stick electrode is consumed in the welding process and becomes part of the weld bead. The flux protects the weld while it cools and is thereafter chipped away by the welder.
Early welding devices included a simple power source, a shielding gas cylinder including an inert gas for TIG, a torch and tungsten electrode (or stinger for STICK) and a work clamp for providing a ground reference for the electrode. The power source of these devices typically included a user-selectable amperage dial for setting a DC output amperage level and a STICK/TIG selector switch for selecting the desired type of welding process. The discovery that welding with the electrode negative (straight polarity) provides deeper penetration, while welding with the electrode positive (reverse polarity) provides better cleaning of oxides from the base metal led to improved welding devices which allowed the welder to select between the two polarities. Further improvements to the early welding devices included offering an AC squarewave output power option wherein the electrode is positive for a half cycle then negative for a half cycle. Further improvements in the AC squarewave output power allowed the user to change the duration of the cycle during which the electrode was negative versus positive, thereby providing an adjustable balance of penetration and cleaning. Because an AC arc was difficult to start and maintain, however, various arc starting modes and arc rectification circuits were created. Before long, the simple welding device of the past had developed into a complex unit with many adjustable functions and options.
As the welder's options in creating, maintaining and controlling the arc have increased, control interfaces and control circuitry have fallen behind. Many welding devices lack adequate control features for assisting the welder in making selections to best start and maintain the arc. Current welding devices utilize hard toggle switches for selecting operating parameters. With increasing options, it is possible for a welder to select an invalid or nonoptimal combination of operating parameters using these hard toggle switches. For example, certain start modes may be invalid in combination with the selected type of welding process or other selected operating parameters. To disable these options, special discrete component circuity must be implemented to prevent malfunction of and possibly even damage to the welding power source. Furthermore, these prior art welding devices are unable to offer preferred selections designed to optimize a particular type of welding process, to store in memory certain parameter settings that the welder may prefer, or to default to certain selections based on the selections of other parameter settings.
Accordingly, a need exists for a welding device that overcomes these and other disadvantages of the prior art. Such a welding device would automatically and selectively disable, enable and default selectors to certain parameter settings based on the selected welding process or the selection of other parameter settings, thus facilitating the setup of the welding device. The welding device would further store selector settings for later recall, such that if input power is interrupted or the welder switches between welding processes during a welding cycle, the welder could immediately return to the previous setup. Moreover, the welding device would also advantageously suggest preferred settings to the welder, thus simplifying the welder's myriad of choices.